1. Field of the Invention
The present invention relates to an engine intake control system which is mounted on a motorcycle, an automobile, an outboard engine system and the like, and particularly to an engine intake control system comprising: an intake passage leading to an intake port of an engine; and an electric motor disposed on one side of a throttle body which rotatably supports a valve shaft of a throttle valve for opening and closing the intake passage, an output shaft of the electric motor being connected to the valve shaft through a speed reduction device for reducing the rotation of the output shaft and transmitting it to the valve shaft.
2. Description of the Related Art
German Patent Application Laid-open No. 10048937A1 discloses an engine intake control system, in which a speed reduction device is housed in a transmitting case to which an electric motor is mounted, and when the transmitting case is coupled to a throttle body, a valve shaft of a throttle valve supported in the throttle body is connected to an output portion of the speed reduction device.
In the conventional engine intake control system disclosed in German Patent Application Laid-open No. 10048937A1, it is possible to assemble, in parallel, a throttle body assembly comprising the throttle body and the throttle valve, and a transmitting case assembly comprising the transmitting case, the electric motor and the speed reduction device, leading to a good assemblability. However, the engine intake control system has the following disadvantages: the throttle body and the transmitting case are constructed completely separately from each other, so that when the throttle body and the transmitting case are coupled to each other, the resulting device tends to be large; and the generation of chattering is not avoided between the valve shaft and the speed reduction device connected to each other upon such coupling. Therefore, there is an insufficient accuracy in the opening degree of the throttle valve by the electric motor.